1. Field of the Invention
The present invention relates to a display apparatus and a control method thereof.
2. Description of the Related Art
Heretofore, in liquid crystal display apparatuses, there is a technique of dividing a screen into a plurality of division regions, and controlling, for each of the division regions, transmittance of a liquid crystal panel (liquid crystal elements that the liquid crystal panel has) and light emission brightness of a backlight (a light emitting unit) in accordance with a characteristic value of a pixel value of an image displayed in the division region (Japanese Patent Application Laid-open No. 2002-99250). By employing such a technique, it is possible to suppress a misadjusted black level of a dark portion of the image, and eventually improve contrast.
Specifically, in display apparatuses required to faithfully reproduce brightness (to maintain the brightness of an image), there is a technique of controlling transmittance of a liquid crystal panel and light emission brightness of a backlight of a division region in accordance with a maximum pixel value of an image displayed in the division region.
However, when the brightness of the image is controlled to be maintained, in a case where small area and high brightness regions (regions with a small area and high brightness) exist in a dark portion of the image as shown in FIG. 3, misadjusted black levels occur in the dark portion. Specifically, in the dark portion, the light emission brightness of the backlight in division regions, in which portions where the small area and high brightness regions exist are displayed, is set to be higher than the light emission brightness of the backlight in division regions, in which portions where the small area and high brightness regions in the dark portion do not exist are displayed. As a result, as shown in FIG. 14, in the dark portion, the portions where the small area and high brightness regions exist are more brightly displayed than the other portions (that is, misadjusted black levels occur).
A conventional technique for solving the aforementioned problem is disclosed in WO 2009/096329, for example. Specifically, WO 2009/096329 discloses that improvement of black expression is attained by determining a scene from an average brightness value of the whole screen and a shape of a histogram, and lowering the light emission brightness of the backlight and reducing an important degree of white portions in a case of a scene with an extremely small ratio of the white portions to the whole screen.
However, in the technique disclosed in WO 2009/096329, the light emission brightness of the backlight of the whole screen is controlled. Due to this, when trying to prevent the aforementioned misadjusted black levels, the brightness on the screen is totally lowered, and faithfulness of the brightness is reduced.